In order to predict the behavior of a design for an integrated circuit, designers and manufacturers (e.g., foundries) often use analog simulation programs such as SPICE. Typically, such a simulation program takes three inputs: (1) a netlist or other description of the integrated circuit's elements (e.g., transistors, resistors, capacitors, inductors, etc.) and their connections; (2) a mathematical device model which describes the integrated circuit using equations; and (3) a description of an input voltage, e.g., from an input waveform.
Some device models implemented in simulation programs have achieved wide acceptance in an industry and have become industry standards. Examples of such device models include Gummel-Poon (GP), BSIM3v3, BSIM4, and PSP. Presently, many of these industry-standard device models are established and maintained by the Compact Model Council. In order to achieve a good fit between the measured data and the simulated data for a device model, modeling engineers set the values of the parameters (e.g., exogenous variables) in the model's equations based on empirical measurements, rather than using default values or ranges associated with the model. These parameters tend to be quite numerous, when fully decomposed. The process of going from empirical measurements to parameter values is called “parameter extraction” and is well-documented. For example, see Franz Sischka, “Modeling a Diode” (Agilent Technologies; Apr. 17, 2001).
Companies such as Agilent and Cadence have developed software/hardware tools to assist with parameter extraction and simulation. A shortcoming of these tools is that they show the output of a simulation (e.g., calculated voltages and currents such as threshold voltage or mobility) in an aggregated form which is not useful for modeling engineers who are attempting to debug or optimize a circuit level design by adjusting the parameter values in a model's equations. Consequently, there is a need for tool that shows the parameter values in intermediate calculations leading up to a simulation output and the results of changing those parameter values.